According to Penn State researchers, plants can trigger a "leaky-gut syndrome" (permeability of the intestinal mucosa) in insects as part of a multi-pronged strategy to protect themselves from ingestion. By better understanding of plant defense, the results could contribute to the development of new pest control methods.

"We have found that a combination of physical and chemical defense mechanisms in maize plants can disrupt the gut barrier of fall worms and allow intestinal microbes to penetrate their body cavities," said Charles Mason, a postdoctoral fellow in entomology. "This can cause septicemia, which can kill the insect or simply trigger an immune response that can weaken the insect."

Researchers culled case worms in the lab and vaccinated them with one of three species of naturally occurring intestinal bacteria. They fed the insects with one of three types of maize ̵

1; one that is known to express enzymes that cause perforation in insect guts. one that is characterized by numerous elongated trichomes or fine hairs that appear on the surface of the plant and contribute to the defense of herbivores; and one that has only a few short trichomes. The team used scanning electron microscopy to investigate the effects of different types of bacteria and maize on the integrity of the worm gut lining.

The scientists found that the presence of all three intestinal bacteria types was the ability of the worms to reduce larvae to damage maize plants, especially when other defense mechanisms such as elongated trichomes and enzymes were present that can perforate both intestinal linings. The types of intestinal bacteria, however, differed in the extent to which they weakened the insects. The findings are published in the July 22 issue of Proceedings of the National Academy of Sciences .

"Our results show a mechanism by which some plants use the intestinal flora of insects in conjunction with their own defense against them," said Mason.

Gary Felton, a professor and head of the Department of Entomology, noted that the findings should have broad implications for understanding the environmental function of plant defense.

"In our study, all of the different plant defense mechanisms, such as leaf trichomes and plant enzymes, require certain gut microbes to defend against herbivores." said. "Our results predict that the variation in plant defense efficacy in nature is largely due to the variability observed in the insect gut microbial communities."

perforation in the intestine of a fallworm. Picture credits: Charles Mason, Penn State

The team said the findings could help inform the development of insect-resistant plants.

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Plants defend themselves against insects by triggering a "leaky gut syndrome" (2019, July 22)
retrieved on July 22, 2019
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